The other day, I was happily tidying up my area - in an off-exhibit area, but still highly visible to the public - when a rather irate gentlemen came up and hollered at me that one of the animals was dead. This was during a pretty busy day, mind you, and when he called that out, crowds stopped and turned. So did I.
Now, the animal in question happened to be a rather geriatric one, so old that it was, at least conceivable, that she could have decided to just plop down and die. That being said, I'd only fed her about an hour ago, plus she was ("is", I should still say) a champion nap-taker, so I had a pretty good idea that she was still among the living. That being said, I immediately put down my shovel and rake and went to check, the complainer in tow (along with a crowd of curious onlookers).
The walk to the exhibit was short, but it proved enough time for my new best buddy to berate me, the rest of the staff, and the zoo in general about our animal care.
How could you not have noticed that this poor animal was dead? I'm pretty sure she isn't, sir.
If you take these animals out of their natural habitat, you've got to at least care for them right. She was born in captivity, sir, part of a managed breeding program. Oh, and as for taking care of her, she's more than twice as old as they usually live in the wild, sir.
Well, we got to the exhibit soon enough, but by then this old crank had been badgering me for so long that I really began to half suspect I was going to find the animal dead. When I got there, I'm ashamed to say, my first thought was, Yep, she's dead. She was stretched out in the sun, eyes open and unblinking, tongue sticking out the corner of her mouth. I called her name, softly. No response. I hopped the fence (keepers only!) and approached the front of the exhibit. I was now close enough to see that she was, in fact, breathing. I called again. This time, she lifted her head, looked at me, and blinked. Why are you waking me up when it's not even feeding time, jerk?, her face seemed to say.
When I turned around, the crowd was dispersing. The "discoverer" of the dead animal was already gone.
So much of what we see of wild animals is on TV and the internet, where the action scenes - the hunts, the fights, the chases, the matings - are emphasized, we tend to forget that animals tend to spend a lot of their day doing not much at all. We seldom see animals in the wild at rest - usually, their sharpened scenes detect our presence long before we see them, so they are alert and wary when we finally lay eyes on them. Zoo animals, however, accustomed to the presence of people, let their guards down. They sleep in front of us... sometimes, very soundly. Sometimes, very very soundly...
If you see a zoo animal that is just lying there, there is probably no need to be concerned... even if the position seems somewhat... suggestive of death. The animals are checked often by their keepers, both at feeding/cleaning time and throughout the day. If you do see an animal that looks like it might not be OK, go ahead and ask a keeper (the keyword being "ask", not "angrily accost and accuse of not caring about their animals"). DO NOT feel the need to "check on" the animal by banging the glass, throwing stuff, or other attempts to make it move.
After all, I know if I was sleeping soundly, I wouldn't appreciate it if people kept interrupting my naps.
"That's right, two dead polar bears, nothing to see here, so keep on going, no noises necessary.."
PS: The step-brother of this "Thing I Never Want to Hear Again" is "Is it real?" This is especially directed towards reptile and amphibian keepers, as well as invertebrate keepers and sometimes aquarists (though I once had a kid who was convinced the kangaroos were fake... as they were hopping).
True, sometimes zoos and aquariums will use models of animals as educational props - Newport Aquarium, for instance, is decorated with life-sized models of manta rays, oarfish, and other marine creatures that it does not exhibit. If it's in a display area with an exhibit label, assume it's real.